Hi and welcome to FixYa, I am Kelly
Everything I am reading says this unit comes with an LPG conversion Kit. It may have been removed by the detailer / retailer that you purchased it from (when ever that was.)
The 0.0354 orfices are supposed to be in the front of the inside of the cooktop and are labeled LP
It is a matter of removing the 4 Natural Gas orifices and installing the LP orfices and then adjusting the air-flow of the grill burner Air Shutters as shown in the manual on page 32.
The center nut has to be removed from the top of the internal gas regulator and the mini post / plunger inverted and then the nut is reinstalled.
Just note that any conversions are supposed to performed by a qualified gas technician as stated by the WARNING in the manual on page 30.
The manual is here:
The step by step instructions are in the product user guide on page 30
or you can go to this link and click on info and guides:
then download the use and care guide.
Thanks for choosing FixYa,